There have been many different types and kinds of computer input devices for entering information into a computer. Certain ones of such devices have enabled users to enter information, such as control information, without the use of a keyboard. Such devices include absolute positioning devices such as light pens and digitizing tablets, as well as relative positioning devices such as joysticks, track balls and mouse devices.
While such prior known accessory input devices may have been satisfactory for some applications, it has been proven to be highly desirable to be able to employ such input devices in an interactive mode with a computer, being used with a projector, such as a conventional overhead projector, to generate video images on a large screen for viewing by an audience. In this regard, when the computer generated images are projected onto a screen in a darkened room, it has been desirable to enable the user to enter information interactively into the computer to modify images, or generate additional images during the presentation. For example, it has been found to be highly desirable to underline or otherwise highlight the images projected onto the screen, or, in general, to select images for display in a nonsequential order.
However, such conventional input devices, such as a mouse device, is not convenient to use during a presentation in a darkened room. Thus, a new optical computer input system has been employed. Such system enables the user to shine a high intensity light onto the screen bearing a computed generated image, to provide auxiliary information for the computer. In this regard, such an input system includes an optical sensing device, such as a charge coupled device camera focused onto the screen. Thus, the system can detect the high intensity light images, and discriminate them from the computer generated images, to input information interactively into the computer, in a convenient manner, even in very low ambient light conditions.
Such an optical system is described in greater detail, in the above mentioned copending parent U.S. patent Ser. No. 07/433,029.
While such a computer input system and method of using it, have proven to be highly satisfactory, it would be desirable to facilitate the initial calibration of the system. Such calibration includes proper alignment of the system, such that the viewing area of the light sensing device or camera of the system, is positioned properly to capture the entire displayed projected computer video image. Such alignment is desirable, because the viewing screen of the system may be positioned at various desired distances and angular positions relative to the system light sensing device.
Also, the calibration of such a system entails sensitivity adjustments. Such adjustments are frequently necessary to accommodate for various different projector light source intensities, as well as various different optical arrangements employed in conventional overhead projectors. Thus, different illumination levels for projected images are possible, and the optical input device requires adjustment of optical sensitivity to the projected image.
Another form of light sensitivity calibration necessary for such an optical computer input system, is the calibration of the system such that it can properly distinguish between background light, and light from the high intensity user controlled light. In this regard, because of variations in ambient background lighting, as well as various different intensity levels of projected high intensity light produced by the projection system, it is desirable to distinguish properly the various light sources, and light images, from the user generated light image, so that the system can properly respond to light information conveyed when the user directs the high intensity light onto the same screen as the computer generated images, for modifying or changing them.
Therefore, it would be highly desirable to have a new and improved apparatus and method to calibrate the alignment and light sensitivity of an optical computer input system. Such an apparatus and method should enable a user to align conveniently the system optical sensing device or camera to capture substantially the entire viewing area of a projected image. The apparatus and method should also enable the light sensitivity of the system to be adjusted so that it can easily distinguish various levels of light, whether produced from a computer generated image, or a user generated light image used to entire user generated information into the computer interactively, even in a darkened room.